The goal is to define mechanisms leading to the development and progression of chlamydiae-mediated atherosclerosis. Approaches will center on studying signaling mechanisms for cLPS and cHsp60, effector molecules known to activate host pro-inflammatory pathways. The hypothesis to be investigated is that cLPS and cHsp60 utilize the Toll-like Receptor-4 (TLR-4) to activate macrophages and endothelial cells via NF-kB and MAPK through myeloid differentiation protein (MyD88). The effects of this activation will lead to increased expression of pro-inflammatory cytokines (IL-6, IL-8), adhesion molecules (ICAM-1 VCAM-1), growth factors (M-CSF), cyclooxygenase-2 (Cox-2) and enhanced transendothelial cell migration of monocytes; all factors implicated in atherogenesis. The hypothesis also will be tested in vivo by determining if apo-E-/-, TLR-4-/- double knockout mice remain indifferent to C. pneumoniae-induced accelerated lesion progression. The specific aims are to (1) determine if TLR-4 is the signaling receptor for cLPS and cHsp60 and to investigate the signaling pathways induced (ERK1/ERK2, p38MAPK and JNK) and other down-stream events leading to NK-kB activation; (2) to define the molecular mechanisms involved in cLPS and cHsp60-induced transendothelial cell migration of monocytes; and (3) to create double knockout mutants in mice (TLR4-/-, apoE-/- and MtD88-/-, apoE -/-) to investigate the contributions of TLR-4 and MyD88 in the initiation and progression of atherosclerosis in the presence and absence of C. pneumoniae infection. The results of these studies are expected to lead to new targets for intervention and prevention of coronary atherosclerosis.